blender pickup up and dropping object -- setting visual keyframes just changes position?
This is the best method I've found pick up and drop and object using the aforementioned child of constraint with an additional copy location and copy rotation constraint on that same object. Then animating the influence siders of the copy location and copy rotation constraint to achieve the desired effect. There is no need to animate the child of influence slider using this method - you can keep the child of influence slider to full strength: 1.000.